Tuesday, June 23, 2009

Wing power in the 33rd America's Cup

[By Lynn Fitzpatrick] The architects of the San Diego Yacht Club America’s Cup defense were considered heretics when they went against the tradition dating back to 1851 and proffered a catamaran rather than a monohull design for 27th America’s Cup Defense. Even within the defense syndicate there was a radical group of designers and engineers who worked diligently to test and prove their theory that wings would perform better than soft sails. At first their theory was scorned, but once they came up with a design that proved to be more powerful than the traditional mast rigged with soft sails, they were accepted. The technology that they introduced earlier in the C-Class, helped to Stars & Stripes chalk up the most lopsided America’s Cup victory in history: a cumulative elapsed time trouncing of over 39 minutes in the two race series.

Copyright Morrelli & Melvin

Over twenty years of technological and materials advancements have passed since that America’s Cup. Some have retired, all have aged in one aspect or another, but one thing has remained constant: Duncan MacLane and David Hubbard have continued to use and perfect wing technology. Among their latest collaborative project is the Autonomous Unmanned Surface Vessel being developed by Harbor Wing Technologies. Not conjoined twins, one is engaged by the Defender and the other is engaged by the Challenger for the 33rd America’s Cup. They are sworn to secrecy. Mark Ott, President of Harbor Wing Technologies, however, was willing to speak about the merits of wing technology.

While mainstream sailors may consider the use of the wings a bit heretical, those in the know and those involved in the arms race to win the America’s Cup are clearly embracing winged technology.

Harbor Wing Technologies X1

The merits of hard winged technology over a traditional mast and soft sails on a multihull, according to Ott:

1) Wings don’t change shape. Sails do. You change the angle of attack to control a wing. You change the sail shape and the angle of attack to adjust sail trim.

2) It is easier to turn a wing on and off by changing the angle of attack than to trim running rigging and soft sails.

3) Wings are more precise and controllable.

4) Wings only have inertial weight; they do not have compressive loading. Masts get out of column very easily and buckle with compression.

5) Without needing to resist the compression loads from a mast shrouds and stays, a winged hull or platform can be much lighter than a traditional hull.

6) Wings are more powerful. Tests performed with Harbor Wing Technologies X1 prototype indicate that in certain wind strengths and directions, a wing is at least two times more powerful than a soft-sailed rig. The effect of slots when using multiple wing elements improves the efficiency of wings.

7) The weight of a mast, rigging, spreaders, halyards, sheets, winches and deck and hull reinforcements to counter the compression forces is comparable to inertial weight of a wing. (Granted, the weight aloft of a wing is slightly greater than that of traditionally rigged sails.)

8)There is less stress on the crew that uses a wing, because they do not haul big sails up and down nor are they constantly trimming.

9) Teams will get take advantage of the best of both worlds on the run when they have the wing element engaged and can hoist a big spinnaker or gennaker to capture the breeze.

If you can’t find footage of the 1988 America’s Cup with one of Stars & Stripes’ hulls gliding through the water while the other barely kisses the surface and New Zealand plods along, take a look at the video of Harbor Wing Technologies X1 at www.HarborwingTech.com or on YouTube. The Harbor Wing seagoing vessels do not have shrouds, because the wing must rotate 360º to adjust to changes in sea states and wind conditions instantaneously. The next generation of manned America’s Cup monster multihulls will have shrouds and that’s where some of the fun will be for spectators. There may be times when the wing is loaded up and the angle of attack can’t be changed quickly or radically enough because of interference from the shrouds.